Preloader for fluid operated devices



Aug. 10, 1943. H. T. KRAFT PREIIOADEH FOR FLUID OPERATED DEVICES Filed Aug. 6, 1942 INVENTOR Herman T. Kraft BY ATTORNEYS Patented Aug. 10, 1943 PRELOADER FOR FLUID OPERATED DEVICES Herman T. Kraft, Akron, Ohio, assignor to The General Tire & Rubber Company, Akron, Ohio, a corporation of Ohio Application August 6, 1942, Serial No. 453,803 Claims. (01. 6054.6)

This invention relates to preloaders for mechanical devices having an inflatable annulus, or. a similarly functioning expansion tube or member, forming a part thereof, as used in brakes,

clutches, couplings, and the like, or the fluid pressure operated type.

The present invention has among its objects the provision of a new and improved fiuidsystem preloader that is positioned at the annulus or expansion member which the preloader maintains charged with a predetermined quantity of fluid so that the brake, for example, is actuated by the transfer of a minimum quantity of fluidbetween the conducting lines of the system and the brake operating mechanism. The small quantity of fluid transferred by the preloader permits the brake or similar mechanism to become engaged and disengaged with a maximum degree of rapidity, efiectualness, power, and control,and permits the use of smaller sized master cylinders that produce higher pressures for the same pedal operation .than similar devices that brake actuating assembly 2 comprises the body portion 4 that has an inner side flange 5, a removable outer side ring 6, and a seat portion 1 that together'deflne an annular flat bottomed groove for receiving an inflatable annulus 8 of rubber or the like.

'nulus 8 by a rubber pad 20. The metal body have been used heretofore. Combined with each preloader is a wear or fit compensating adjustment that is adapted for the accurate and positive adjustment of the friction shoes of the device. The preloader is positive and self-operating in a pressure fluid system. It is compact and simply installed. The preloader is 01 small size and light weight and consists of parts that are simply designed, rugged in construction, and dependable in operation.

With the above and other objects in view that will be apparent to those skilled in the art, from the following discussion, the embodiment of the present invention is shown as applied'to a vehicle brake, and is illustrated in the accompanying drawing, wherein:

Figure 1 is a fragmentary side elevation, with parts broken away, of a preloader that embodies the present invention as applied to a vehicle brake and showing in section portions of the preloader, the expansible annulus, and the brake drum;

Fig. 2 is a fragmentary axial section of the brake preloader, taken along the line 22 of Fig, 1, showing the expansion tube in its pre- "'1 that is carried by a vehicle wheel (not shown) and'the brake actuating assembly 2 that is carried by the torque plate '3 of the-vehicle. The

Brake blocks 9 are carried bysheet metal saddle members ID, the legs II of which straddle the inflatable annulus 8 and are held in place by torque pins I2 that extend through the outer wall I3 of the annulus and through-suitable apertures in the legs I I of the saddle members I0. The ends of the torque pins I2 extend into suitable radial slots I5 and I6 that are formed respectively in the inner side flanges 5 and the outer side ring 6 to carry the braking torque directly from the brake block through the saddle to the torque disc or plate 3.

The preloading device comprises a metal body member I9 that is secured to the inflatable'anmember I 9 has a cylindrical bore 2|, one end of which opens intothe cavity of the annulus 8 and the opposite end of which has a fluid inlet port 23 but is otherwise closed in any desired manner, as by the plug22. Braking fluid flows through the fluid inlet port 23 toward or away from the device through the supply tube 24 that is attached to the body member I9 of the preloader in any suitable manner, as by the fitting 25'or the like.

A cylindrical piston member 26 is mounted for reciprocating motion within the cylindrical bore 2I of the body member I9. The piston 26 has a channel 21 extending therethrough for conducting braking fluid into and out of the inflatable annulus 8. The piston 26 terminates at one end in a valve 28 through which the fluid channel 21 opens. The valve 28 may be a part of a single piece piston or it may be formed as a part of a removable packing ring 29 that makes threaded engagement with the body portion of the'piston 26 as shown to compress packing 38 between the pitson body and the bore of the body member I9. For certain uses, such as on vaircraft brakes, for instance, the packing member may be dispensed with because one operation of the brake will preload the system even when there is substantial leakage past the piston body. The other end of.

- member 26 toward the cylindrical bore 2I of the body member I9 and against the resilience of the helical compression spring 32. The spring 32 is supported at its lower end by the plug 22. Suitable means, such as crossed channels 33 and 34 in the head of the piston 28, permit unrestricted flow of the pressure fluid between the cavity of the annulus 8 and the piston fluid channel 21 that terminates in the valve 28.

Suitable means, such as an adjusting bolt 48, that threads through the plug 22,- serves to adjustably position the valve seat 38 with respect to the valve 28 part of the piston 28. The valve seat 38 is mounted in a valve seat cup 38 on the end of the bolt 40. By means of this arrange- .ment, the valve seat 38 may be adjusted toward or away from the valve 28 to compensate for wear or for adjustment of the brake shoes 9 relative to the brake drum I. The valve seat 38 is secured in its adjusted'position bya locking nut 4| that threads into the plug 22. The adjusting bolt 40 is sealed against leakage by means of the packing 38 that is interposed between the locking nut 4| and the plug 22. A gasket 31 is interposed between the plug 22 and'the body member IQ for the same reason.

In the position shown in Fig. 2 of the accompanying drawing, the radially outer wall l3 of the inflatable annulus 8, yieldingly bears against the head 3| of the piston 28 to maintain the valve 28 closed against the valve seat 38. When the piston 26 is in this position, the braking fluid within the annulus cavity and the piston fluid channel 21 is It is to be understood'that the particular constructions shown, the. particular assembly of parts, and the mode of operation and the results of the embodiment of the invention that are oppositely positioned walls that are separated by the inflation thereof comprising in combination, a body member carried by one of said oppositely positioned walls and having a cylindrical bore opening into the inflatable member at one end and closed at the other end except for a fluid inlet port, a cylindrical piston member reciprocable within said bore and having a fluid channel extending from end to end thereof, one end of said piston member terminatin in a valve into which said fluid channel opens and the other end OI saidpiston member having parts'for engagement with the other of said oppositely positioned walls, a valve seat carried by the body member and arranged for engagement with the valve or said piston member to open and close said fluid v cnamiel, and means for adjusting said valve seat entrapped therein-and the brake shoes 9 are held just out of engagement with the brake drum I.

Whenthe supply tube conducts high pressure braking fluid from the braking systeminto the valve compartment of the preloader, the

brake shoes 9 against the brake drum l with a degree of force that is proportional to the pressure to which the braking fluid is subjected.

Upon the release of pressure in the supply tube 24, the excess braking fluid in the annulus 8 passes through the crossed channels 33 and 34 in the head 3| of the piston 28, through the fluid conducting channel 21 in the piston 28, out of the mouth of the valve 28, and into the tube 24, until the pressure of the outer wall l3 of the annulus 8 on the head 3| of the piston 28 seats the valve 28 on its valve seat 38 to entrap the residual braking fluid in the annulus cavity ahead of the valve 28 and thus maintain the annulus 8 sufficiently full of the braking fluid to hold the brake shoes 9 in a position that assures a minimum clearance between the brake shoes 9 and the brake drum I."

When the frictional surfaces; of the brake shoes wear away or get out of adjustment, the lock nut 4| may be loosened, and the valve seat adjusting bolt 40 rotated in the plug 22 to elevate the valve seat 38 and thereby maintain the desired clearance between the brake shoes and the drum. The locking nut 4| is then tightened to maintain the valve seat 38 in the desired position with respect releasable couplings for machine parts and for other applications where preloading of an expansion member is desired.

toward and away from said inflatable member.

2. A preloader for an inflatable member having oppositely positioned walls that are separated by the inflation thereof comprising in combination, a body member carried by one of said op-- positely pos1tioned walls and having a cylindrical bore opening into the inflatable member at one end and closed at the other end except for a fluid inlet port, a cylindrical piston member reciprocable within said bore and having a fluidchannel extending from end to end thereof, one end of said piston member terminating in a valve into which said fluid channel opens and the other end of said piston member having parts for engagementwith the other of said oppositely positioned walls, a valve seat carried by the body member and arranged for engagement with the valve of said piston member to open and close said fluid channel, means for adjusting said valve seat toward and awayjfrom said inflatable member, and spring means interposed between said piston and the closed end of said body member to urge said piston member toward the other of said oppowhich said fluid channel opens and the other end i of said piston member having parts for engagement with the other of said oppositely positioned walls, packing means interposed between said piston member and said cylindrical bore for minimizing the leakage of fluid therebetween, a valve seat carried by the body member and arranged for engagement with the valve of said piston member to open and close said fluid channel, and means for adjusting said valve seat toward and away from said inflatable member.

and closed at the other end except for a fluid inlet port, a cylindrical piston member reciprocable within said bore and having a fluid channel extending from endto end thereof, one end of said piston member terminating in a valve into which said fluid channel opens and the other end of said piston member having parts for engagement with the other of said oppositely positioned walls, a packing interposed between said piston member and the cylindrical bore in, said body member for maintaining a substantially fluidtight relation therebetween, a packing ring engaging said piston for exerting pressure on said packing, a valve seat carried by the body member and arranged for engagement with the valve of said piston member to open and close said fiuidchannel, and means for adjusting said valve seat toward and away from said inflatable member.

5. A preloader for an inflatable member having oppositely positioned walls that are separated by the inflation thereof comprising in combination, a body member carried by one of said oppositely positioned walls and having a cylindrical bore opening into the inflatable member at one end and closed at the other end except for a fluid inlet port, a cylindrical piston member reciprocable within said bore and having a fluid channel extending from end to end thereof, one end of said piston member terminating in a valve into which said fluid channel opens and the other end of said piston member having parts for engagement with the other of said oppositely positioned V walls, a packing interposed between said piston member and the cylindrical bore in said body member for maintaining a substantially fl'uidtight relation therebetween, a packing ring en-- gaging said piston for exerting pressure on said packing, a valve seat carried by the body member and arranged for engagement-with the valve of said piston member to open and" close said fluid channel, means for adjusting said valve seat toward and away from said inflatable member, and spring means interposed between said piston and the closed end of said body member to urge said piston member toward the other of said oppositely positioned walls of the inflatable member.

, HERMAN T. KRAFT. 

